Fossil fuels, particularly oil and gas, are the primary sources of heat for conventional gas turbines. One of the critical factors in selecting a fuel for gas turbines is its heating value (HV). Traditionally, gas turbines have relied on high-calorific fuels such as natural gas. However, recent estimates indicate that the reserves of these fossil fuels are limited, necessitating the exploration of alternative energy sources. Biofuels emerge as a promising sustainable option, with their combustibility demonstrated at both laboratory and pilot scales. Despite this potential, challenges such as atomization and the emission of nitrogen oxides (NOx) persist, hindering their widespread exploitation in current gas turbine engines. Nuclear energy is another potential heat source for gas turbines, but commercial nuclear plants traditionally operate on the steam Rankine cycle. Ongoing research on high-temperature gas reactors aims at enabling their use with closed cycle gas turbines, potentially expanding nuclear energy's role in future power generation.